The present invention relates to a rapid, semi-quantitative test method for the determination of levels of C-reactive protein in biological fluids.
C-reactive protein (CRP) is a prototypic acute phase protein in humans that increases rapidly in concentration as a result of tissue injury, inflammation or infection. The normal range of serum CRP is 0.08-3 milligram (mg) per liter (l). However, CRP levels can increase between 100-1000-fold during an inflammatory response. Elevated serum levels of CRP are seen 6-12 hours (h) after an inflammatory stimulus, and maximum levels are reached within 48-72 h. Generally, CRP levels will return to normal 55-10 days after remission of inflammation. Because the accumulation of CRP in serum closely parallels the course of inflammation and tissue injury, CRP has been used as a diagnostic tool to detect inflammation and to monitor the clinical course of various diseases. For example, CRP levels are found to exceed 50 mg/l in rheumatoid arthritis, systemic lupus erythematosus (SLE), ulcerative colitis, Crohn""s disease, acute pancreatitis, cardiac infarction, septicemia, bacterial meningitis, and pneumonia.
The standard test for CRP in the clinic in the United States is by rate nephelometry using the Beckman Array system (Beckman, Fullerton, Calif.) with a detection limit of 10 mg/l. Other methods including turbidimetry (Multistat, Instrument Laboratory, Lexington, MA) and fluorescence polarization immunoassay are also used in European countries. Commercial ELISA kits for measurement of low levels of CRP are also available but are not used clinically because the procedures are lengthy require special instruments/reader, and trained technicians to perform the assay. The choice of method will be determined by a number of factors. For large hospitals and diagnostic laboratories, automated, quantitative determination of CRP can be performed with specialized instruments by highly trained technicians. Typically, physicians"" ordered CRP tests are performed in a centralized diagnostic laboratory and turnaround time of a day or so is normal. Latex agglutination and Nycocard (Nycomed Pharma AS, Oslo, Norway), methods that have been developed in recent years for CRP measurements that can be performed in the physician""s office, are faster, although not necessarily more accurate alternatives.
Therefore, there is a need for a rapid, sensitive, and accurate assay for the measurement of CRP levels in biological fluids such that the assay can be conducted in a physicians office or on site and does not require costly equipment or highly skilled personnel to operate the instruments.
The present invention satisfies the need discussed above. The present invention relates to an accurate, fast, dip-stick method for assaying and quantitating the amount of CRP in a biological sample. The assay has particular application to serum samples and can be conducted at the location where the patient is found and does not require sophisticated equipment.
The assay is a multiple tube procedure using a solid support coated with polyclonal antibodies to CRP in which the solution of the final tube will result in a color change of the solid support where presence of intense color will indicate high levels of CRP in the serum and faint color will indicate low levels of CRP in the serum. The assay reagents, pipettes/dropper, and test tubes may be provided in the form of a kit.